1. Field of the Invention
The present invention relates to an optical sensor unit which is utilized for a picture processing apparatus such as a scanner or the like and in which a plurality of light receiving sections of respective CCD sensors are arranged in a manner of a straight line so that the picture processing apparatus is used as a line sensor.
2. Prior Art of the Invention
Conventionally, in a line sensor utilized in a scanner or the like of a picture processing apparatus, it has been requested to read a manuscript or a copy which is wide in width in recent years. An optical system which reads the manuscript utilizes a CCD which executes photoelectric transferring of an incident light which has read the manuscript. Under the present condition, it has been difficult to manufacture a single CCD capable of reading the manuscript wide in width, easily and at a low cost. In order to magnify or enlarge the reading width, a line sensor has been utilized in which a plurality of CCD sensors are used, and light receiving sections thereof are arranged in a single row.
FIG. 8 of the attached drawings shows a cross-sectional arrangement of an optical sensor unit that is the above-described line sensor.
As shown in FIG. 8, an optical sensor unit 1 comprises an elongated frame 2 for being mounted on an apparatus (not shown), a plurality of CCD sensors 3 whose respective light receiving sections are arranged in a single straight line, and ceramic substrates 4 on which the CCD sensors 3 are arranged and which is fixedly mounted along a longitudinal direction of the frame 2. In this case, the plurality of ceramic substrates 4 are arranged on and fixedly mounted on the frame 2 so that the plurality of light receiving sections of the respective CCD sensors 3 are arranged in a single straight line. Thus, a single line sensor is formed.
With the above-described arrangement, it is difficult for the ceramic substrates 4 to process the same for being mounted on the apparatus (not shown). For this reason, the ceramic substrates 4 have been arranged on the frame 2 which uses a metal material such as an aluminum or the like which is relatively easy in processing for being incorporated into the apparatus (not shown). Further, the CCD sensors 3 are arranged on the ceramic substrates 4 and are fixedly mounted thereon. In this case, the ceramic substrates 4 and the frame 2 are bonded or adhered to each other by adhesives 5 and are fixedly mounted to each other by the adhesives 5.
However, for the optical sensor unit 1 arranged as described above, the frame 2 and the ceramic substrates 4 are different in coefficient of thermal expansion from each other, and the frame 2 expands or contracts by a change in circumferential temperature so that a stress is generated with respect to the ceramic substrates 4. For this reason, spaces or intervals between the plurality of CCD sensors 3 arranged in one straight line shift from each other.
By the way, spaces or intervals between the picture elements of the CCD sensors 3 are approximately 20 .mu.m. In a case where the light receiving sections of the plurality of CCD sensors 3 are arranged on the frame 2 so as to be brought to one straight line to form a line sensor, displacement of the light receiving sections with respect to a light incident direction does not come into question. However, positional shift in one straight line of the light receiving sections of the plurality of CCD sensors 3 comes into question. That is, the intervals between the plurality of CCD sensors 3 shift slightly so that discontinuous portions occur on the way of reading information of one line.
As described above, the conventional optical sensor unit has a problem that the frame 2 expands or contracts by the change in circumferential temperature so that a stress occurs with respect to the ceramic substrates 4. Thus, it is impossible to accurately detect the incident light by the shift which occurs due to the stress.